1. Field of the Invention
The present invention relates to an image forming apparatus using electrophotography, such as, for example, a copier, a printer, or a facsimile system.
2. Description of the Related Art
In recent years, image forming apparatuses including an electrophotography apparatus have been upgraded in pursuit of high-speed processing, full-fledge functionality, and advanced color capability. Various types of printers and copiers have been placed on the market.
Above all, an in-line image forming apparatus capable of forming color images at a high speed is expected to become the mainstream of color printers in the future. The in-line image forming apparatus has a plurality of image forming means, each of which handles a different color, arranged in series with one another, and successively transfers toner images to superimpose them on one another. The in-line image forming apparatus falls into two types. Referring to FIG. 4, one type of in-line image forming apparatus transfers color toner images successively from photosensitive drums 109M, 109C, 109Y, and 109K onto a transfer medium 101, which is borne and transported by a transfer/transport belt 107, and thusly superimpose the images on one another to produce a color image. Referring to FIG. 5, the other type of in-line image forming apparatus first transfers color toner images successively from the photosensitive drums 109M, 109C, 109Y, and 109K onto an intermediate transfer belt 150. The in-line image forming apparatus then transfers the plurality of color toner images transferred onto the intermediate transfer belt 150 onto the transfer medium 101 all together, and thus produces a color image.
In the image forming apparatus having the transfer/transport belt 107 or intermediate transfer belt 150, when unnecessary toner remains and adheres to the surface of the belt, it causes the back of the transfer medium 101 to be soiled. This also causes images produced by the apparatus to be stained. Specifically, toner adheres to the transfer/transport belt 107 or intermediate transfer belt 150 during a sequence of steps of transferring a color mismatch detection toner image or a density detection toner image from the photosensitive drum to the transfer/transport belt 107 or intermediate transfer belt 150, and then checking the toner image. The sequence is carried out in order to control paper jams, fog-causing adhesions of toner to non-image portions, color mismatches, and toner density.
The toner remaining or adhering to the transfer/transport belt 107 or intermediate transfer belt 150 is removed by cleaning means (cleaning blades) 160 and 170.
However, according to a conventional cleaning method for removing toner that remains or adheres to the transfer/transport belt 107 or intermediate transfer belt 150, a waste toner container used to collect waste toner removed by the cleaning means 160 and 170 is necessary. The waste toner container is needed separately from a waste toner container used by cleaning means 114M, 114C, 114Y, and 114K for removing toner remaining on the photosensitive drums 109M, 109C, 109Y, and 109K. This results in a large-sized cleaning unit and necessitates the complex structure of the apparatus, thereby leading to an increase in the cost of the apparatus, thereby leading to an increase in the cost of the apparatus.
Accordingly, an object of the present invention is to provide an image forming apparatus capable of removing toner from a transfer medium bearer so as to clean the transfer medium bearer.
Another object of the present invention is to provide an image forming apparatus capable of removing toner from an intermediate transfer member so as to clean the intermediate transfer member.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.
In accordance with the above objects, there is provided an image forming apparatus, including a movable image bearing member for bearing a toner image and a movable transfer medium bearing member for bearing a transfer medium. A toner image borne by the image bearing member is transferred onto a transfer medium borne by the transfer medium bearing member at a transfer position. The difference between the moving speed at which the image bearing member passes through the transfer position and the moving speed at which the transfer medium bearing member passes through the transfer position when the toner image is transferred from the image bearing member onto the transfer medium is unequal to the difference in moving speeds when toner on the transfer medium bearing member is transferred onto the image bearing member. The inequality of these differences enables the apparatus to have improved cleaning efficiency as well as improved image transfer efficiency.
The aforementioned differences in moving speed, or the moving speeds themselves, may vary according to whether the image bearing member or the transfer medium bearing member is passing through the transfer position. The mathematical relationship between these moving speeds may conform to one of several inequalities. The difference may be substantially zero when the toner image on the image bearing member is transferred onto the transfer medium.
The image forming apparatus may also include a transferring means for transferring the toner image on the image bearing member onto the transfer medium. The transferring means may also be used for transferring toner on the transfer medium bearing member onto the image bearing member.
The image bearing member may include several image bearing elements. Images on the image bearing elements may successively be transferred onto the transfer medium, thus superimposing the images upon one another. An electric field induced for transferring toner from the transfer medium bearing member onto the first image bearing element may have a direction that is opposite to the direction of an electric field induced for transferring toner from the transfer medium bearing member onto the second image bearing element.
The image forming apparatus may also include a collecting means for collecting toner from the image bearing member.
In another embodiment of the present invention, an image forming apparatus includes a movable image bearing member for bearing a toner image and a movable intermediate transfer member. A toner image borne by the image bearing member is transferred onto the intermediate transfer member at a transfer position, and then the toner image is transferred from the intermediate transfer member onto a transfer medium. The difference between the moving speed at which the image bearing member passes through the transfer position and the moving speed at which the intermediate transfer member passes through the transfer position when the toner image is transferred from the image bearing member onto the intermediate transfer member is unequal to the difference in moving speeds when toner on the intermediate transfer medium is transferred onto the transfer medium.